The field of the present invention is apparatus and methods for buoyantly supporting an aircraft upon the surface of a body of water. More particularly, the present invention relates to flotation bags which are normally disposed deflated upon the landing skids of a helicopter, and which are inflated in order to support the helicopter when ditching or landing on water is anticipated.
Conventionally, helicopters making flights over water have employed flotation bags assembled to and packed in a deflated condition upon the landing skids of the helicopters. Typically, such conventional flotation bags are attached directly to the helicopter landing skids, and are then folded or packed tightly within flexible fabric covers. Such an assembly procedure requires considerable time during which the helicopter is unavailable for service. Periodic inspection and maintenance of the flotation bags also requires that the helicopter be removed from service while the bags are unpacked, inspected, repaired or replaced, if necessary, and then repacked on the landing skids.
Another consideration with conventional flotation bags is the possibility for one or more of the bags to become trapped between the helicopter fuselage and a landing skid during inflation. This possibility is exacerbated when the flotation bags are deployed while the helicopter is exposed to a cross wind. In such a situation, one or more of the flotation bags on the upwind side of the helicopter may be blown between the helicopter fuselage and the upwind landing skid as they are inflated. When these flotation bags reach full inflation they are trapped beneath the helicopter. If the helicopter is subsequently forced to ditch upon water, the buoyancy provided by the flotation bags may be sufficiently misplaced with respect to the center of gravity of the helicopter that capsizing is more likely, or is certain to occur.
Yet another shortcoming of conventional helicopter flotation bags is their propensity to flutter or oscillate when inflated with the helicopter in flight. In the event the bags become accidentally inflated in flight, or are inflated as a precaution against an engine difficulty which is transient, it is desirable for the helicopter to be able to maintain a relatively high airspeed despite the inflated flotation bags. In many cases, conventional flotation bags prohibit the use of the full speed capability of the helicopter with the bags inflated because of flutter of the bags which could cause structural damage to the helicopter, or destroy the flotation bags, or both.